The present invention concerns polymers containing at least one succinimide ring substituted on the nitrogen atom by a reactive group, where the ring is supported either by the main chain or by a side chain.
The properties of the polymers of the present invention are improved compared with polymers which do not contain a succinimide ring substituted on the nitrogen atom by a reactive group. In particular, they have improved adhesive properties and can thus be used as surface coatings. They are also more heat resistant than the polymers from which they are derived.
The polymers of the present invention have reactive groups which allow them to be used in the production of polymer alloys.
The polymers of the present invention can be defined as polymers containing at least one succinimide ring substituted on the nitrogen atom by a reactive group, the ring being supported either by the main chain or by a side chain, the polymers resulting from reacting at least one polyolefin obtained from at least one unsaturated monomer selected from ethylene, butenes and norbornenes, with at least one compound containing a maleimide ring substituted on the nitrogen atom by a reactive group with formula xe2x80x94Rxe2x80x94(X)n where X is a reactive group, n is a number equal to 1 or more and R is a residue containing at least one carbon atom. Usually, n equals 1 and in this case the compound containing a maleimide ring used in the present invention is represented by formula 1 below: 
The reactive group xe2x80x94X is generally selected from a hydroxyl group, a carboxylic group, a carboxamide group, a carboxylic acid halide group, a thiol group, a thiocarboxylic group, an amino group, a halogen, an epoxy group, and an esterified carboxylic group in which the ester portion contains a reactive group. When a plurality of xe2x80x94X groups are present, they can be identical or different.
Very often, the reactive group is selected from groups which can react with epoxy functions by opening the oxirane ring. Usually, compounds containing a reactive group are used which are selected from a carboxylic group, a carboxamide group and an acid halide group, for example a carboxylic acid chloride group. The preferred group is the carboxylic group.
The group xe2x80x94Rxe2x80x94 is normally selected from the group formed by saturated or unsaturated, substituted or unsubstituted aliphatic hydrocarbons, and substituted or unsubstituted aromatic groups. In general, unsubstituted groups are preferred, normally groups containing at least one aromatic nucleus. Examples of groups which are frequently used are benzenic groups which are bonded in the ortho, meta or para position to the nitrogen atom and to the reactive group xe2x80x94X. Normally, the para or meta form is used.
The polyolefins used to produce the polymers of the present invention can be formed by homopolymerisation or copolymerisation of at least two monomers.
In one particularly preferred form, the polyolefin is selected from the group formed by high density polyethylenes and ethylene copolymers which are preferably constituted by at least 90% of ethylene moieties and at most 10% of a C3 to C8 olefin. More particularly, high density polyolefins are used which preferably have a density of about 0.9 to about 0.97 and a fusion index measured in accordance with standard ASTM D-1238 of about 0.2 to about 100 (measurements carried out under a 19.6 kg load at 190xc2x0 C.).
The polymers of the present invention are prepared bringing a molten polyolefin into contact with at least one compound containing a maleimide ring substituted on the nitrogen atom by a reactive group in a mixer or extruder. This preparation can be carried out with or without a radical initiator. Examples of radical initiators are peroxides. Preferably, a radical initiator is not used in the present invention. This possibility of forming, without a radical initiator, polymers containing a succinimide ring substituted on the nitrogen atom by a reactive group, the ring being supported either by the principal chain or by a side chain, constitutes a distinct advantage of the present invention which avoids the risk of cleavage and cross-linking of the polymer. The reaction temperature is normally in the range from about the fusion temperature of the polyolefin to about 300xc2x0 C. This temperature is usually about 200xc2x0 C. to about 260xc2x0 C. The reaction time is relatively short and normally does not exceed 10 minutes. An extrusion-reaction system is normally preferable as it produces very good results.
The present invention also concerns the use of the polymers described above for the production of surface coatings. These polymers, with good adhesive properties, are more suitable than the starting polyolefins for this application. These polymers can also be used to produce alloys of polymers, in which the reactive function improves formation of the alloys. They can also be used for the production of co-extruded products. They can also be used for the production of multi-layered materials.